Dados do Trabalho

Título

MICROBIOLOGICAL EVALUATION OF RAW, EXTRUDED, ROASTED, AND PRE-COOKED WHOLE-GRAIN PEARL MILLET FLOURS

Introdução

Pearl millet grains are rich in fiber, proteins, and minerals. Processes such as roasting, pre-cooking, and extrusion can enhance the physicochemical, sensory, and microbiological quality of this cereal, resulting in a variety of food products. This study aimed to assess the impact of extrusion, roasting, and pre-cooking on the microbiological counts of whole-grain pearl millet flours.

Material e Métodos

Whole pearl millet grains were cleaned and ground to obtain raw flour, and then processed as follows: I) extrusion using a twin-screw extruder equipped with a circular-shaped matrix with a single 8 mm diameter hole and a two-blade cutter with a temperature profile from feed to exit of 25, 25, 60, 90, 120, 120, 120, 90, 60, and 60 ºC; II) roasting in an oven at 150 ºC for 15 minutes; and III) cooking in boiling water at a 1:2 grain-to-water ratio for 35 minutes, followed by dehydration and grinding. Microbiological analyses included counts of aerobic mesophiles, enterobacteria, total coliforms, Escherichia coli, presumptive Bacillus cereus, molds and yeasts, as well as testing for the presence of Salmonella.

Resultados e Discussão

The samples showed absence of Salmonella/25 g and counts of E. coli and presumptive B. cereus <10 and <102 CFU/g, respectively. Thus, all samples complied with regulatory standards. The raw flour significantly differed (p<0.05) from the processed flours, exhibiting the highest contamination levels of enterobacteria (6.19 log CFU/g), total coliforms (5.69 log CFU/g), mesophiles (6.04 log CFU/g), and molds and yeasts (4.40 log CFU/g). There was no significant difference (p>0.05) among the extruded, roasted, and pre-cooked flours in terms of enterobacteria (1.85, 1.00 and 1.00 log CFU/g), total coliforms (1.95, 1.00 and 1.00 log CFU/g), mesophiles (1.39, 2.10, and 1.48 log CFU/g), and molds and yeasts (2.00 log CFU/g for all).

Conclusão

Therefore, heat-treated samples demonstrated lower contamination levels compared to raw flour, indicating their suitability for various food production applications.